Electric glass furnace



June 27, 1950 P. ARBEIT 2,512,761

- ELECTRIC Guss FURNACE Patented vJune 27, 1950 ELECTRIC GLASS FUBNACEPierre Arbeit, Paris, France, assigner to Societe Anonyme desManufactures des Glaces et Prcduits Chimiques de Saint-Gobain, ChaunyCirey, Paris, France Application August 5, 1947, serial Nu. 766,277

In France January 16, 1946 Section 1, Public Law 690, August 8, 1946Patent expires January A16, 1966 1o claims.' (01.13-6) This inventionrelates to glass making and has particular relation to improvements inthe manufacture of glass by a continuous process in which the glassundergoes in sequence the melting of the raw materials, the fining ofthe melt, and the cooling of the very hot lined glass to a temperaturesuitable for working. A particularly valuable phase of the invention isrelated to glass furnaces of electric type wherein heating current threezones roughly corresponding to the three said phases of manufacture.Frequently, some l of the zones are combined, but in the more modernfurnaces barriers have been erected in an attempt to isolate the threesteps of the process. Nevertheless, it has been diicult to control thetemperature at which the glass is received in the working zone or toinsure the dissolving of small glass bubbles that do not escape from thefined glass before the solidication of the glass in the form of anobject. Y

The operation of cooling, also called conditioning, has as an object tobring the glass from thevery high fining temperature at which it is veryuid to a lower working temperature at which the glass may beconveniently employed in the fashioning of objects. It also has as anobject to dissolve the small gas bubbles that have not escaped duringiining. It has been desirable that the machines which shape the glassarticles should be fed by glass at uniform temperature. However,heretofore these conditions have not been attained perfectly orcontinuously, and whenA attained at all, have been attained onlyimperfectly or with very great difllculty and by the use of compartmentsof large size and at the cost of maintaining, at high temperature,larger bodies of glass than are needed for the normal operation of themachines. The absorption of bubbles has been attained only by keepingthe glass in the lining tank for a long period of time so that theconvection currents will eventually lead to the homogenizatlon of theglass and the absorption of the bubbles.

It is an object of this invention to produce more homogeneous glass.

. Another object is to provide for the absorption and solution of smallbubbles into fined glass so as to produce a bubble-free product.

Another object is to eliminate or materially reduce wandering glasscurrents.

Another object is to employ the convection currents arising fromdifferences in temperature in the glass in combination with new furnacestructure to attain useful ends, for instance to facilitate the transferof glass from step to step of the process.

Another object is to reduce the size of the chambers in a glass furnace.v

Another object is to reduce the cost of heating by reducing the massesof the glass subjected to heating and by reducing the time of heating.

Another object is to employ electrical heating by submerged electrodesto facilitate the other objects of the invention and to acquire a newand more perfect continuous process of making glass.

The objects of the invention are accomplished, generally speaking, by aprocess that includes forming a ning pool of molten glass, fining theglass in the lining pool, withdrawing fined glass from the ning pool tothe upper part of a. settling pool, allowing the withdrawn glass tosettle and cool in the settling pool until gas bubbles have beenabsorbed and the temperature of the glass is right for working, andwithdrawing glass from the settling pool to a Working pool. The newfurnace involves a chamber in which the iining of the glass occurs, aworking chamber, and between them a separate settling chamber that isconnected to the fining chamber by a passage at the upper part of thesettling chamber, and to the working chamber by a passage at the lowerpart of the settling chamber.

Under such conditions it has been proved thatv the cooling of the glassis uniformly effectuated without the need of giving large dimensions tothe compartment, and this permits in consequence to obtain a coolingthat is both uniform and quick.

This result might be explained by the fact that the glass, when it iscooled, tends to descend and consequently tends of itself both towithdraw from the orifice of entry and to approach the orifice ofdischarge from the compartment, but it does not reach the orifice ofdischarge except as it becomes sufficiently cool and at the sametemperature as the glass which has already gathered before this orifice.Iniother words, the process tends togive automatically to the due toconvection, movements which are produced in the usual installations andwhich are otherwise indispensable for the making of lhomogeneous glassby a kind of working, but which are naturally diiiicult to control.There is no longer danger that there will be set up across theconditioning zone currents of hotter glass capable of establishingdiierences in temperature in the glass that issues, as is the case inprior art installations where, as is known, the glass enters the lowerpart and issues from the upper part. Furthermore, there is no ylongerdanger that cool glass, having traversed the whole conditioning zone andhaving arrived at a proper temperature before the outlet orifice, willreturn into the ning zone because that would require the cold glass torise in the conditioning compartment and repass the orifice by which itentered the compartment. There is thus prevented a movement of the glasswhich would have for its consequence to increase the quantity of glassthat passes from the fining compartment into that of conditioning and torequire of the latter to cool more glass than is necessary to feed themanufacturing machines. It should be understood that in practice theconditioning compartment conforming to the invention might be associatedwith auxiliary compartments interposed between that compartment and thecompartment which precedes it and the compartment which follows it; thatis to say, the lining compartment and the one from which the glass iswithdrawn. Such auxiliary compartments might be necessary in eiect inorder to associate the conditioning compartment contemplated by theinvention with the different types of ning compartments or of workingcompartments. The essential is that, after ning, the cooling of theglass should take place in larger part in a compartment designed inconformity with the principles of the invention. Different ways ofaccomplishing the invention are given hereafter by way of non-limitativeexamples, reference being had to the attached drawings which represent:

Fig. 1 is a schematic vertical longitudinal section through that portionof a glass furnace that includes a new settling chamber.

Fig. 2 is a similar section through a furnace employing a singlemelting-iining compartment ln combination with the new settlingcompartment.

Fig. 3 is a similar section through a furnace having a separate ningcompartment in which heating is accomplished by a combination of flameand electricity.

Fig. 4 is illustrative, by a similar section, of a furnace havingadvanced control of glass currents.

Fig. 5 is a similar section through a furnace of further modied form.

In the furnace illustrated in Fig. 1 the numeral I indicates the tank inwhich the operations of melting, iining, settling, and working occur.The numeral II shows the dome of the furnace. It is to be presumed thatthis furnace is constructed in a normal manner so far as the materialsof its construction are concerned. At one end of this furnace is amelting zone I2, a filling zone I3 and a port for the admittance ofmaterials I4. Heating is accomplished in this instance by resistors Iwhich are submerged in the glass at a level related to that of anorifice is provided in a tame n that extends across the furnace andseparates the two zones I2, I3 from the settling pool that isestablished between the baffle I'I and the baille I8. The orifice I6which l gives admittance to the fined glass from the ning pool isnearthe top of the settling pool in the form of Fig. l, but the orificeI6 is completely submerged. The baille I8 has an orifice I9 that is nearthe bottom of the settling pool 20. Thus the hot fined glass enters atthe top of the settling pool and is cooled as it sinks in the pool untilit approaches an ideal working temperature as it passes through theorifice I9. The working compartment 2l has a kind of narrow passage orflue 22 through which the glass passing orifice I9 makes its way intothe pool 23 from which the glass is withdrawn for shaping. This flue maybe used if desired to cool, Still further, the glass from thetemperature at which it passes through orifice I9. It is advantageousgenerally speaking to vconstruct and arrange the walls of thecompartment containing pool 20 in such manner that in any one horizontalplane the four walls of the compartment exercise a like cooling effectupon the glass.

It is particularly to be noted, and this forms a part of the presentinvention, that the wall I'I is between the very hot glass of the finingcompartment and the cooler glass of the settling compartment, whichwould tend to make this wall hotter than the other walls of the settlingchamber. This problem has been solved by the conceptions of Fig. 2. Inthat figure the construction of the furnace is similar to Fig. l exceptthat the wall I'I that separates the melting-lining compartment from thesettling compartment extends upwardly from the bottom of the furnace toa position just below the level of the glass, so that a shallow vchannelexists between the iining and settling compartments through which theglass passes from the top of the one to the top of the other at the rateprovided by the withdrawal of the glass through the discharge port 24.The three electrodes Ia, I5b, I5c are so arranged, across themeltingning compartment, that they constitute a barnier to the passageof unmelted particles and of unfined glass toward the channel above wallIl'. The very hot ned glass moving from the vicinity of electrode I5cpasses over the wall I 'l' to the top of the settling chamber and slowlysinks as it cools through the chamber until it passes through theorifice I9 into the flue 22.

In Fig. 2 another diierence appears in that wall I'I' is hollow and isprovided on the side of the lning chamber with heat insulation 25 and onthe side of the setting chamber with a water jacket 26 through whichcooling water at selected temperature may be passed in order to preventthe glass in the settling chamber', in the vicinity of the wall, frombeing kept at too high a temperature to serve satifactorily in theworking chamber.

In the structure of Fig. 3 two walls 30, 3| isolate the fining chamberfrom the melting chamber to the left and the settling chamber to theright. Between these two walls are located two electrodes 32, 33 whichmaybe of Joule effect type if desired. These electrodes are suiilcientlyspaced from the walls of the furnace so that the relatively cool unnedglass coming from the compartment I2 over the wall 30 tends because ofincreasing density as it cools to sink to the bottom of the compartment,whereas the hot currents rise about and particularly toward the rightside of the electrodes attaining a very high temperature as they ascendand ridding themselves of the major portion of their occluded gaseswhich leave the surface of the very fluid glass in bubbles. Thesuperimposed relation of the electrodes, which may be as many in numberas desired, tends to produce a superheating of the process which isquite beneficial at this stage. This very hot glass passes over thebarrier 3| at the rate provided by the withdrawal of glass through theport 24 to the top of the settling chamber in which it descends at therate provided by the size oi the chamber and the rate of withdrawalthrough port 24 until it reaches the bottom. During its settling andpassage through the settling chamber, the glass cools and the tinebubbles that were not liberated inthe fining chamber are dissolved inthe glass, providing a glass at the entrance to the working chamber thatis bubble-free. The arrows indicate the approximate path of the glasscurrents through the fining compartment. In this form of the inventionthe heating of compartment I2 is by gas flame burners 34. In addition,the surface o! the glass in the flning chamber is also heated by alia-me burner 35.

In the structure described in Fig. 4 the tank is provided with adepending barrier 40 and an upwardly projecting barrier 4I. Thedepending barrier terminates short of the bottom of the furnace so thata passage exists through which glass from the melting chamber may passto the iining chamber. With the lining chamber are electrodes 42operating by Joule eil'ect which project vertically through the bottominto and beneath the surface of the glass in the ilning chamber. Theseelectrodes initiate currents of very hot glass that ascend toward thetop of the lining chamber, are prevented from returning to the meltingchamber by the baille 40, and flow over the top of the submerged baiile4I into the settling chamber 20. The arrows indicate the general courseof the glass flow through the several chambers, and it will be observedfrom the arrangement and construction of these chambers that there willbe a marked reduction in the iiow of uncontrolled convection currentsthroughout the furnace.

In Fig. 5 the melting chamber l2 is separated from the ning chamber bymeans of a baille 43 which projects upward from the bottom of the tankand has a shallow channel through which the glass from the meltingcompartment may flow to the top of the lining compartment. A dependingbaiile 44 projects downwardly from above the level of the glass in theflning chamber to a position toward the bottom thereof. Between thesetwo baflies are located electrodes 45 operating by Joule effect whichsubject the glass in the iining compartment to high temperature. Thecurrents from these electrodes ascend into the space between baiiles 43and 44 so that the glass between those baffles is subjected to acontinuous working by high temperature convection currents. The glass iswithdrawn from the fining compartment beneath the baille 44 and enters akind of flue 46 provided between baille 44 and a baiiie 41 projectingupwardly from the bottom of the furnace to a position beneath the levelof the glass. Ihe fined glass taken from the flning compartment passesthrough the ue 46 and over the baffle 41 to the top of the settlingchamber 20 wherein it is progressively cooled as it settles and absorbstiny bubbles that did not escape during the previous steps of theprocess.

It is generally to be noted that the glass which is admitted to thecompartment 20 is taken directly from the surface of the ningcompartment, that is, from the level where the largest gas bubblesescape and from which the cooling and the absorption of little bubblesshould commence. In other terms, the major part, if not the entirety ofthe cooling from the temperature of flning is eilectuated in theconditioning chamber, under conditions of stability conducive to theattainment of a superior result.

It is to be noted that the types of furnace such as those represented inFigs. 3, 4, and 5 in which the heating is made simultaneously by nameburners and by electric current in the mass of glass lend themselvesparticularly well to the accomplishment of the process, which lies inaccomplishing by heating means exterior to the glass such as by flameburners a heating which is simply adapted to attain as well in thecompartment of fusion as in that of fining a relatively low temperaturein the neighborhood of the temperature of conditioning, while there isestablished in the flning compartment within the body of the mass ofglass, by the passage of electric current, the higher temperaturenecessary to complete the fusion and to obtain the lning.

It should be understood that it is not excluded from the spirit of theinvention to employ in the conditioning compartment auxiliary heatingmeans such as flame burners, radiant heaters and electric current in theglass to assist in regularizing the attainment of a good glasstemperature. Similarly, heating means may be added to the compartment 23to produce certain local effects used in different types of glassmanufacture.

The invention contemplates:

l. A continuous process for making glass in accordance with which glassis made to pass successively through different compartments wherefusion, flning, conditioning, or cooling are accomplished, the processlying in conditioning the glass in a compartment in which the glass athigh temperature which issues from the ilning compartment enters theupper part and issues from the lower part.

2. Furnaces for the accomplishment of the process following (1)characterized by the following points taken separately or incombination:

a. The glass passes from the fining compartment to the conditioningcompartment by a channel which connects the two compartments in theupper part of the bath.

b.' After conditioning the glass enters the compartment of withdrawalthrough a vertical conduit of small section, which it enters from thelower part of the conditioning compartment.

vc. The conditioning compartment is associated with a. fusion and finingcompartment heated by the passage of an electric current introduced byhorizontal electrodes localized in the upper part of the bath.

d. The conditioning compartment is associated with a lining compartmentwhich communicates with the compartment of fusion by a channel in theneighborhood of the surface of the bath and which is heated by thepassage of an electric current introduced by horizontal electrodes someof which are situated above others above the depths and near the surfaceof the bath.

e. The conditioning compartment is associated with a nning compartmentwhich communicates with the fusion compartment through the lower part ofthe bath and which is heated by the passage of the electric currentintroduced by vertical electrodes passing through the bottom of thecompartment into contact with the lower part of the bath.

f. The conditioning' compartment is associated with a lining compartmentwhich communicates with the fusion compartment through the upper part ofthe bath and which is heated by the psage of electric current introducedby electrodes vertically localized in the lower part of the bath, atransverse wall being provided in the lining compartment on the sidefrom which the glass discharges, to constitute a kind of verticalconduit taking the glass from the lower part of the ning compartment tolead it to the upper part of a conditioning compartment.

As many apparently widely different embodiments of the present inventionmay be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the speciiicembodiments, except as dened in the appended claims.

What is claimed is:

1. The process of glassmaking that includes the steps of establishingseparated ning, settling, and working pools of molten glass having acommon surface level, electrically heating substantially the entirewidth of the upper level of the glass in the ning pool, said ning pooldischarging from its upper level horizontally to the upper level of thesettling pool, said settling pool discharging from its lower level, witha change of direction, substantially vertically to the working pool.

2. The process according to claim 1 in which the glass discharged to thesettling pool is taken from beneath the surface oi' the ning pool.

3. The process according to claim 1 in which the glass discharged to thesettling pool is taken from the surface of the ning pool.

4. The process according to claim 1 in which a stream of glass is takenfrom the bottom of the nning pool, moved vertically, and dischargedhorizontally to the top of the settling pool.

5. A glass furnace including a chamber in which occurs the ning of glassand comprising electrical means for the heating of the glass bath, aseparate settling chamber connected to the said chamber by a passageextending from the upper level of the glass in the ning chamber into theupper level of the glass in the settling chamber, and a separate workingchamber connected to the settling chamber through a vertical passageissuing from the lower part of the settling chamber, the structuralrelationship of the chambers and passages comprising means to provide a.common glass surface level throughout the furnace.

6. The furnace of claim 5 in which the upper passage is whollysubmerged.

7. The furnace of claim 5 in which the upper passage is open.

8. The furnace of claim 5 in which the settling chamber is separatedfrom the upstream zones by a wall arising from the bottom almost to thesurface of the glass, and a dipping bridge wall extends therebefore fromabove the surface almost to the bottom, whereby ned glass passeshorizontally beneath the bridge wall, vertically between the walls. andis horizontally discharged over the settling chamber wall to the top ofthe settling chamber.

9. The furnace of claim 5 in which at least a submerged electrode in theupper part ci the nning chamber acts as a barrier to the travel of unnedglass toward the passage opening into the settling chamber.

10. The furnace of claim 5 in which the ning chamber is electricallyheated by means of submerged vertical electrodes penetrating through itsbottom wall.

PmRE ARBEIT.

REFERENCES CNED The following references are of record in the ile ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 12,323 Richardson Feb. 28,1905 248,109 Fetters Aug. 23, 1881 972,778 Sauvageon Oct. 11, 19101,552,555 Gravel Sept. 8, 1925 4@ 1,593,054 Arbeit July 20, 19261,611,328 Arbogast Dec. 21, 1926 1,656,510 Cornelius Jan. 17, 19281,820,248 Raeder Aug. 25, 1931 1,880,541 Wadman Oct. 4, 1932 1,905,534Wadman Apr. 25, 1933 1,944,855 Wadman Jan. 23, 1934 2,068,925 MulhollandJan. 26, 1937 2,277,678 Borel Mar. 31, 1942 2,283,188 Cornelius May 19,1942 2,283,800 Ferguson May 19, 1942 2,397,852 Gentil Apr. 2, 19462,413,037 De Voe Dec. 24, 1946 FOREIGN PATENTS Number Country Date250,536 Great Britain July 29, 1926 Certiicate of Correction Patent No.2,512,761 June 27, 1950 PIERRE ARBEIT It is hereby certied that errorappears in the printed specification of the above numbered patentrequiring correction as follows:

Column 5, line 33, for the Word With read Within;

and that the said Letters Patent should be read With this correctiontherein that the seme may conform to the record of the case in thePatent Ooe.

Signed and sealed this 19th dey of September, A. D. 1950.

[SEAL] A THOMAS F. MURPHY,

Assistant O'ommz'ssone?A of Patents.

Certificate of Correction 'Patent No. 2,512,761 June 27, 195ok PIERREARBEIT It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows:

Column 5, line 33, for the Word With read Within;

and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Oce.

Signed and sealed this 19th day of September, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents.

